The regulation and physiologic role of urinary kinins in normal and disordered states of water balance will be studied using a new radioimmunoassay for bradykinin. Specifically, the potency and mechanism(s) of action of vasopressin induced kininuresis will be determined and compared to those for other hormones and drugs that affect or are affected by salt and water balance. Urinary kallikrein and kininase also will be measured to determine if changes in either account for the kininuretic actions of vasopressin or other stimuli. Patients with neurogenic or nephrogenic diabetes insipidus will be studied during vasopressin infusion to determine if the regulation of urinary kinin is abnormal in either condition. Finally 2 drugs that increase or decrease kinin excretion by a vasopressin independent mechanism will be studied to determine how they affect the regulation of antidiuretic function. The results of these studies may suggest new approaches to the study and/or treatment of certain disorders of salt and water balance.